Cassini has now completed 20, out of 22, of its daring plunges through the empty space between Saturn and its inner rings. It was about seven years ago when the project decided to make use of this extraordinary opportunity. Mission designers discovered the option and presented it as an elegant way to end the mission at a time when most of the spacecraft’s propellant would be used up. Among the many options studied, the Cassini Project Science Group judged the Solstice Mission as by far the most scientifically rewarding …